I definitely agree about Bird Song and it's open-nature. In fact a number of Bird Songs, esp. from 72-73 sound like mini Dark Stars to me. I too wish they had played this (along with a number of tunes like Here Comes Sunshine) in '74, the potential seems endless.
Anyways, I have always thought fall of '72 was the very best time for this song. There's also some fantastic ones from Spring/Summer '73 and of course the acoustic ones are beautiful. Here's a few of my favorites that weren't mentioned: